1. Field of the Invention
The present invention relates generally to an automatic transaxle in a power train of an automotive vehicle. More specifically, the invention relates to a supporting structure and bearing structure for a rotary component, such as a rotary output shaft, of an automatic transaxle.
2. Description of the Background Art
One example of the conventional output shaft bearing structure for an automatic transaxle has been disclosed in "AUTOMATIC TRANSAXLE RN4F02A Type and RL4F02A Type Service Manual 1984", issued by Nissan Motor Company, Limited. In the disclosure of the above-identified publication, a counter shaft is provided in parallel relationship with an output shaft of an automatic power transmission section of the automatic transaxle. The output shaft of the transmission section is coupled with the counter shaft via an output gear and a counter gear. The counter shaft is connected to a differential gear unit. The output shaft and the output gear are formed integrally to each other. Such output shaft is supported by means of a pair of taper roller bearings.
Such prior proposed bearing structure is, however, not, completely satisfactory in terms of durability. Namely, the aforementioned structure of the bearing structure has a drawback in that wearing of the taper roller bearings is too substantial for lowering power transmission efficiency. In addition, one of the taper roller bearings oriented at the end of the output shaft is placed within a bearing receptacle groove formed in the output gear so as to reduce axial size. The presence of the bearing receptacle groove in the output gear definitely lowers rigidity of the output gear to cause gear noise.
Also, in the aforesaid disclosure, the support structure includes a retainer fixed onto a wall of a transmission casing. The output shaft as a rotary component of the automatic power transmission, extends through the retainer and is rotatably supported therein. A clutch drum is supported on the outer periphery of the retainer. A working fluid is supplied to the clutch drum through a fluid path defined through the transmission casing and the retainer.
In the prior proposed construction of the support structure as set forth above, a further drawback is encountered in that the configuration of the retainer becomes complicated and thus requires relatively large radial and axial sizes. Specifically, the retainer is positioned relative to the transmission casing by fitting the outer diametric section onto the wall section of the transmission casing. The retainer is rigidly fixed onto the transmission casing by means of fastening bolts extending through a flange section having a larger diameter than the outer diametric section. Such construction requires sufficient radial size of the retainer. Furthermore, the fluid path for supplying the working fluid to the clutch drum extends through a portion where the retainer and the transmission casing are interengaged with one another. As a result, it becomes necessary to form radial and axial fluid paths through the retainer. This necessarily expands the axial size of the retainer.